Treatment of turbid liquids



July 26, 1949. E. M. KELLY TREATMENT OF TURBID LIQUIDS 2 Sheets-Sheet 1 Filed Dec. 10, 1946 Y INVENTOR. [Tar/ M A d/g July 26,1949. 5, KELLY 2,477,459

TREATMENT OF TURBID LIQUIDS Filed Dec. 10, 1946 2 Sheets-Sheet 2 INVENTOR. y far/ M. Ke/lg H 7'TORNE Y Patented July 26, 1949 UNITED STATES PATENT A OFFICE 'raaa'rmmv'r r glam LIQUIDS Earl M. Kelly, Los Angeles, Calif. Application December 10, 1946, Sfl'ifll N0. 715,309

4 Claims.

This invention relates to a process and to an apparatus for the treatment of turbid liquid such as may be provided by raw sewage heavily laden with solids or a like liquid. In fact, the apparatus and process of the present invention are particularly suited to the treatment of such a turbid liquid.

. It is the generally broadobject of the present invention to provide a novel process and a novel apparatus for the treatment of a turbid liquid heavily laden with solids having a relatively high biological oxygen demand as a raw sewage.

Another object of the present invention is to provide a process for the treatment of raw solid laden sewage to the end that the biological oxygen demand of such sewage maybe quickly reduced and satisfactory clarification of the water effected in a relatively short time whereby the operation can be conducted in a vessel having such a volume relative to the rate of flow that the retention time is relatively short.

The invention includes other objects and features of advantage, some of which, together with the foregoing will appear hereinafter wherein the present preferred form of process of this invention is disclosed in coniunction" with suitable Figure 1 thereof, I have shown a tank 8 of generally circular outline and having a bottom 1 extending inwardly and sloping downwardly to a sludge pocket 8 and a sludge outlet line Q. Mounted concentrically with respect to the tank 6 is a circular shell supported by hangers l2 from a beam |4 extending transversely of the tank; the shell is supported with its lower edge spaced from the tank bottom and its upper edge extending above the normal liquid level in the tank. An influent line It extends through a side wall l5 of the tank to discharge within shell ll. Clarified liquid is removed through ellluent pipe I1, the overflow liquid being collected by a trough It, to which the eflluent pipe I1 is connected. A

hollow shaft 2| is suitably supported in a bearing (not shown) on beam |4 andby a combined steady bearing and thrust bearing 22 positioned on the tank bottom. Amotor on the beam H A plurality of radial arms rotates the shaft 2|.

23 extend from the hollow center shaft 2|, each of the arms having a plurality of jet openings 24 therein. The upper end of shaft 2| is connected to an air inlet line 26 so that air admitted to the shaft 2| passes down through the shaft and out through the several arms 23 for release through the several jets 24. Each of the radial arms is secured and supported by a brace 29 from a collar 3| provided upon the hollow central shaft. The air can also be released from porous plates or tubes, if desired.

Also mounted upon and extending radially from shaft 2| are a plurality of sludge rakes indicated generally by numeral 32 and supported from a collar 33 on the hollow shaft 2| by braces 34. The sludge rakes are each formed to rake the sludge along the sloping tank bottom I to discharge the sludge finally into the sludge pocket 8.

In operation, heavily laden raw sewage, for example, is discharged through line I6 into the agitation-aeration compartment provided by the interior of the stationary inner compartment while shaft 2| is rotated and air is released through the jets 24 to pass upwardly through the released sewage to sweep any odors in the sewage out of the sewage, to satisfy the biological oxygen demand and to eifect a desired coagulation or coagmentation of solids therein. The solids which settle past theseveral arms 23 are of a settleable size and remain on the bottom of ,the tank to be moved along by the sludge rakes toward the sludge pocket 8. The sludge rakes positively return the settled sludge from the sedimentation compartment to the agitation compartment. Immediately upon entrance to this compartment a portion or all of the returned sludge will be raised by virtue of the air lift action of the introduced air and will be immediately mixed and circulated with the other contents of this compartment. It hasbeen found in practice that the maintaining of a large volume of circulating solids tends to accelerate bacterial action with the consequent increase in rate of purification. Also the settling characteristics of the solids in the liquid are greatly improved, permitting rapid sedimentation in the outer compartment. .There will be, of course, some sludge which will be positively raked to the sludge outlet but this, in main,

will be the denser, heavier material which resists the circulating currents induced by the air. In the activated sludge process, aeration and sedimentation are carried out in separate tanks. Sludge from the sedimentation tankis continuously pumped back to the aeration tank for aeration in contact with the incoming solids. In the mentation characteristics of the liquid returned.

amuse device of the present invention, this is accomplished by the operation of the sludge rakes. In the operation of sedimentation units on sewage, it

is not possible to hold sludge in. sedimentation units beyond a few hours because of the decom- 5 posing tendencies of the organic material present, which usually results in decreased purification and a floating of a considerable portion of the sludge load. For'this reason the average c'larifier, whether primary or secondary, in sewage treatment maintains detention periods within narrow limits of a few hours and sludge is removed usually every four hours or at least once every 24 hours. The introduction of air in theocenter compartment of the device of the present invention, combined with the positive pulling in of sludge from the outer sedimentation compartment, permits the holding of sludge for an indefinite period of time, since the, air satisfies the A oxygen demand tendencies and maintains the solids in a fresh state. This has considerable advantages in that it is'pos'sible to build up an appreciable concentration of solids which has a beneficial effect on both the purification and sedi- Normally the liquid level in tank 6 is maintained at the height of trough .l8 and below the upper edge of shell II so that any eiiiuent liquid issuing from the shell i I must pass out-between the lower end of the shell and the bottom of the tank to issue finally into the sedimentation compartment provided between the shell I! and tank 6. In this manner, the biological demand of the heavily solid laden sewage can be readily satisfied, the desired flocculation or coagmentation of the finely divided solids present'in sewage can be effected, the gases present in the sewage swept out and the biological demand of the sewage and of the turbid liquid satisfied to the end that finally there can be discharged a clarified liquid in a relatively short period of time.

Referring to that form of the invention shown in Figure 2, I have there indicated a-suitable tank 5| having a bottom 52 sloping inwardly and downwardly to a sludge pocket 53 and from which sludge can be removed through line 54.

Centrally of the tank 5| is provided an influent conduit indicated generally by numeral 56 and connected to an influent conduit 51 through which is introduced the heavily laden raw sewage or other turbid liquid. The upper end of conduit 56 is secured to a beam 56 which extends outwardly from a carriage 59 mounted for movement alongside wall 60 of the tank5i by motor 16'. Mounted concentrically in the tank and surrounding the conduit 56 is a tubular .shell 65 sealed from the conduit by suitable sealing means indicated generally by numeral 6!. 'A plurality of hollow tubular arms 62 extend radially from the tubular shell 65, each of the arms having a plurality of jet openings 63 thereinto release air admitted to the interior'of the arms. Each of the arms 62 is additionally supported from the tubular shell by suitable braces. An

4 until the sludge falls into the sludge pocket 65.

The interior of the shell 61 provides an agitation-aeration compartment while the region between the shell 61 and the tank 6| provides a sedimentation compartment. Sludge falling to the bottom of tank 6| beneath either the sedimentation compartment or the agitation compartment is moved by sludge rakes ll into sludge pocket 63.

in operation, the infiuent is admitted through line 61 and issues from the infiuent column 66 and through the shell 66 through the apertures 6| and 62 therein. At the same time, air is admitted through the several Jets 63 into the radially extending arms 62 to sweep out'any gases carried in the influent liquid, to satisfy any biological oxygen demand of the liquid, to coagment or fiocculate settleable solids in the fluid. IE-re infiuent liquid, of course, displaces some of the liquid in the agitation compartment, the displaced liquid passing between the shell 61 and the bottom of the tank upwardly into the sedimentation zone in which further sedimentation and coagmentation may take place until finally, the eflluent liquid is collected and discharged by treugh 63 into theeilluent line 64. The rotation of the air discharge arms 62 and the sludge rakes ensures thorough and uniform treatment of the liquidjn the tank. I claim: 1. Apparatus for sewage treatment comprising a tank, a hollow shaft rotatably mounted centrally of said tank a plurality of arms extending radially from said shaftto a point intermediate said shaft and the outer wall of the tank, and spacedabove but adjacent to the tank'bottom, sediment discharge means for discharging sediment, a plurality, of radial sediment rakes extending from said shaft to closely adjacent said tank, wall to move sediment on the tank bottom to said sediment discharge means, air discharge means on said radial arms, means for supplying air to said'air discharge means, outflow means by which clarified liquid is drawn of! adjacent the outer tank periphery, an annular shell supported on the radial arms adjacent the ends of the radial arms and extending above the elevation of the from the lower periphery of the tank to the sediment discharge means, the combination which comprises an upright central shaft in the tank, means for rotating the shaft, a hollow air discharge arm fastened rigidly to the shaft and extending outwardly in the tank part way to the periphery and above the rake arm, the, air discharge arm being perforated along its length at a plurality of points, means for supplying air under pressure to, the air discharge arm through the shaft, an, annular baflle disposed in the tank adjacent the path of the outside end of the air discharge arm and extending from a level immediately .above the rake arm to a level above that of the liquid discharge, and means for introducing the sewage to be treated into the space within the baille.

3. In sewage treatment apparatus having a tank, sediment discharge means in the bottom of the tank near the center, liquid outflow means at the periphery of the tank near the top, and a rake arm disposed just above the tank bottom and rotatable about its center to move sediment from the lower periphery of the tank to the sediment discharge means, the combination which comprises an upright central shaft in the tank,

means for rotating the shaft, a hollow air discharge arm fastened rigidly to the shaft and extending outwardly in the tank part way to the periphery and above the rake arm, the air discharge arm being perforated along its length at a plurality of points, means for supplying air under pressure to the air discharge arm through the shaft, an annular baflle supported -by the air discharge arm and disposed in the tank adjacent and, rotatable about its center to move sediment from the lower periphery of the tank to the sediment discharge means, the combination which comprises an upright central shaft in the tank, means for rotating the shaft, a hollow air discharge arm fastened rigidly to the shaft and extending outwardly in the tank part way to the periphery and above the rake arm, the air discharge arm being perforated along its length at a plurality of points, means disposed within the shaft for supplying air under pressure to the air discharge arm through the shaft bottom, an annular baille disposed in the tank adjacent the path of the outside end of the air discharge arm and extending from a level immediately above the rake arm to a level above that of the liquid discharge, and means for introducing the sewage to be treated into the space within the EARL M. KELLY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,138,349 Mallory Nov. 29, 1938 2,223,257 Mallory Nov. 26, 1940 2,355,069 Green Aug. 8, 1944 2,400,598 Prager May 21, 1946 2,404,701 Felsecker July 23, 1946 

